Polish freedom icon Lech Walesa on Wednesday left hospital after undergoing a series of cardiac tests in the northern city of Gdansk.

The 73-year-old Nobel peace laureate, who suffers from high blood pressure, had planned to attend an anti-government street protest on Monday but was forced to sit it out after being hospitalised over the weekend.

"Now he has to rest. He won't be going to his office in the next few days," a member of his staff, who wished to remain anonymous, told AFP.

While in hospital, Walesa announced that he planned to attend the next anti-government demonstration in Warsaw, scheduled for August 10.

The demonstrations are being held in opposition to a monthly march carried out by governing Law and Justice (PiS) party leader Jaroslaw Kaczynski in memory of his twin brother Lech, Poland's president at the time, and 95 other people who were killed when the presidential jet crashed in Russia in 2010.

The Polish government is being probed by the European Union over perceived threats to the rule of law, and Walesa has previously questioned whether Kaczynski is seeking to turn Poland into "a dictatorship".

Shipyard electrician Walesa won the Nobel Peace Prize in 1983 for leading Solidarity, the Soviet bloc's only free trade union, and became Poland's first democratically elected president in 1990.

His boldness in standing up to the communist regime is still widely respected, but his divisive presidency earned him scorn from many Poles.